Certain organisms can be utilized as a source of oil such as triglycerides in the production of biofuels. For example, algae naturally produce triglycerides as energy storage molecules, and certain biofuel-related technologies are presently focused on the use of algae as a feedstock for biofuels. Algae are photosynthetic organisms, and the use of triglyceride-producing organisms such as algae provides the ability to produce biodiesel from sunlight, water, CO2, macronutrients, and micronutrients. Algae, however, cannot be readily genetically manipulated, and produce much less oil (i.e., triglycerides) under culture conditions than in the wild.
Like algae, Cyanobacteria obtain energy from photosynthesis, utilizing chlorophyll A and water to reduce CO2. Certain Cyanobacteria can produce metabolites, such as carbohydrates, proteins, and fatty acids, from just sunlight, CO2, water, and inorganic salts. Unlike algae, Cyanobacteria can be genetically manipulated. For example, S. elongatus PCC 7942 (hereafter referred to as “S. elongatus PCC 7942”) is a genetically manipulable, oligotrophic Cyanobacterium that thrives in low nutrient level conditions, and in the wild accumulates fatty acids in the form of lipid membranes to about 4 to 8% by dry weight. Cyanobacteria express light harvesting protein (LHP), which collects photons (i.e., light energy) and channel their energy to the photosynthetic reaction centers. However, although these proteins are extremely efficient at harvesting light, their capacity to use light for photosynthesis is easily saturated.
Clearly, therefore, there is a need in the art for modified photosynthetic microorganisms, including Cyanobacteria, capable of performing improved photosynthetic activity and producing oil such as triglycerides, e.g., to be used as feedstock in the production of biofuels and/or various specialty chemicals.